1. Field of the Invention
The invention relates to an ablation catheter for the generation of linear lesions in the myocardium, comprising an elongated catheter body, which has a proximal and a distal end; and a linear, substantially cylindrical ablation electrode on the distal end of the catheter body.
2. Background Art
As for the background of the invention, it can be said that catheter ablation is a frequently used therapy for the treatment of certain arrhythmias. A lesionxe2x80x94a sort of tissue removal or scarxe2x80x94is generated at a certain position in the myocardium by the aid of the ablation electrode of the catheter, interrupting the defective electrical stimulus conduction that is responsible for the arrhythmias. Linear lesions are in particular produced for the treatment of atrial flutter or fibrillation.
Applying energy to the cardiac tissue via the ablation electrode takes place either by high voltage direct current (DC) or by electromagnetic radiation in the radio frequency rangexe2x80x94which has recently become the preferred method, owing to DC problems. A fundamental requirement in ablation therapy resides in the precise placement of the ablation electrode within the heart.
Conventional ablation catheters of a first basic design comprise unipolar ablation electrodes of point action so that they have to be displaced frequently for individual ablation steps if linear i.e., elongated, lesions are to be generated. This is time-consuming and comparatively inaccurate because of the local inaccuracy of the position of the ablation electrode within the heart. Another design which has been improved in this regard resides in ablation catheters having multipolar electrodes of point action, the individual poles of which are to be triggered sequentially by an especially suitable ablation control system.
U.S. Pat. No. 5,676,693 teaches an ablation catheter for the generation of linear lesions, which produces a longitudinal, quasi liquid electrode by means of conductive fluid emerging from the catheter and several electrodes placed therein.
U.S. Pat. No. 5,800,428 teaches an ablation catheter for the generation of linear lesions, which has a thin, elongated wire-type ablation electrode on the distal end. In a special design, several combined wires are provided as ablation electrodes on the distal end, spread up two- or three-dimensionally. In this case, the electrode wires may be electrically insulated from each other.
Finally, U.S. Pat. No. 5,676,662 teaches an ablation catheter for the generation of linear lesions, in which the ablation electrode consists of a spirally coiled conductor with spaced turns; this conductor is partially embedded in the catheter body and covered also from outside by an insulating layer which is recessed along a longitudinally parallel strip for the outside of the spirally coiled conductors to lie open. In this area they constitute the ablatively effective, linear zone of the electrode.
In this ablation catheter it is provided to make part of the turns of the ablation electrode separately triggerable so that the separated conductor pieces are suitable to serve as a scanning electrode for the detection of electrocardiologic signals before and after the actual ablation processxe2x80x94for the so-called mapping. As a result of this configuration, various sections of the spiral electrode section can detect or scan various sections of the myocardium without displacement of the spiral electrode.
The known ablation electrodes have in common that, owing to the limited or non-existent possibilities of scanning electrocardiogic signals, the accuracy of positioning leaves much to be desired.
It is an object of the invention to further develop an ablation catheter of the generic type such that the ablation electrode has improved positioning properties.
This object is attained by at least one sensing electrode being embedded in, and insulated from, the jacket of the ablation electrode.
As a result of this combination of ablation and sensing electrode, it is possible to produce a longitudinal lesion in a single ablation job by the linear ablation electrode. The substantial disadvantage which resides in that these longitudinal electrodes usually are hard to position because they do not offer sufficient perceptivity lengthwise is suppressed by the additional sensing electrode. While, in the case of sensing by a long electrode, the electric excitation front when spreading through the myocardium integrates towards zero in terms of signal implementation along the long electrode, the sensing electrode, which is embedded in the ablation electrode, can be made very short and thus highly perceptive and locally specific.
Another advantage in the use of a single elongated ablation electrode is the fact that a conventional, single-outlet standard ablation generator can be used for making the ablation energy available that is needed for the generation of an elongated linear lesion.
Preferred embodiments of the ablation catheter according to the invention are specified in the sub-claims. Further features, details and advantages of the invention will become apparent from the ensuing description of exemplary embodiments of the invention, taken in conjunction with the drawings.